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HUANGHUACHENG, China (Reuters Life!) - The Great Wall of China is greater than previously thought, according to a recent technologically advanced survey of the World Heritage site.
China's most thorough investigation of the wall to date has shown that in the Ming Dynasty era, it stretched 8,851.8 km (5,500 miles), further than the previous estimate of around 6,000 km (3,700 miles).
According to the joint survey by the State Administration of Cultural Heritage (SACH) and the State Bureau of Surveying and Mapping, the massive structure is comprised of 6,259.6 km of wall, 2,232.5 km of natural barriers such as rivers and mountains, as well as 359.7 km of trenches.
Chen Jun, president of the National Geomatics Center who helped map the wall in three-dimensions for the survey, said the findings were important to the future of the wall, one of China's most famous symbols.
"This is significant because the Great Wall is like a name card for the Chinese people. People who have never come to China all know the Great Wall," Chen said.
"If we know how long the wall is and where it is located then we can protect it properly. So it really is very important."
Chen and other researchers spent over two years surveying the wall, using GPS positioning systems, infrared technology and other mapping techniques, to create the most comprehensive picture to date.
It shows that the easternmost point of the wall in fact lies at Hushan in Liaoning province as opposed to Shanhaiguan in coastal Tianjin. The survey was part of a 10-year project to conserve the structure launched in 2005.
The new, detailed maps should help protect sections threatened by range of factors, Chen said.
"We see that the entire length of the Ming Dynasty era Great Wall was 8,851.8 kilometers, but now perfectly restored parts only make up between 10 and 20 percent of that," Chen said.
"There are some parts where the state of preservation is worrying. Large-scale construction poses a threat, and in history erosion and war have also taken their toll."
The wall now mostly lies in short stretches, with many areas either in ruins, blown away or dissected by roads and new developments.
Around 2,000 km, almost one third, of the original wall has vanished altogether, according to the SACH.
At the Huanghuacheng section, an area popular with tourists, a dam and a public road cut through the ancient structure. Visitors climb wilder, crumbling sections that are not officially open to the public and stretches have become popular sites for summer raves.
Construction first started on the wall over 2,000 years ago, but it was only in the Ming Dynasty (1368-1644) that it was extended and sections were linked together into a continuous barrier against northern invaders.
The survey now plans to do more research into Qin and Han Dynasty portions of the Great Wall, and will finish in 2010, organizers said.
Editing by Miral Fahmy and Nick Macfie